Recently I've had a problem on my home machine where when right clicking on various shell items (not every shell item) could take 1-2 minutes to bring up the context menu. Explorer would go 'Not Responding', yet take up 0% CPU. Obviously something was blocking in Explorer, and I figured it to be one of my context menu handlers. Context menu handlers are buried within the registry in an expansive set of keys for literally every type of file system object on your computer. Locating every context menu handler is a tall order, but with a little help from Google, I found that NirSoft has an amazing tool called ShellExView which allows you to view all hooks into the Shell, and disable them en masse.
The first step I took was disabling every Context Menu and Property Sheet handler. Then I restarted my machine, and prepared to slowly re-enable them until I found the offending handler. ShellExView has a cool sort method to sort by company, which I tried first, but found no relief. Eventually I discovered that no matter how many things I disabled, my context menu was still slow as dirt.
Then I cut off my network card. Windows loves to take its time trying to find UNC paths--as you're well aware if you've ever mistyped a network share into Start/Run--so I chanced to gather that some shell verb pointed to something on a network path that was no longer there. Viola! Without a network connection my shell context menu's came up at regular speed.
How on earth do I easily find the culprit? There is some shell verb with a UNC path being referenced, and the Registry is a mighty large place. Once again NirSoft1 came to the rescue with their Registry search tool RegScanner. Set it to search for "\\" and stand back for the deluge of UNC paths found in your registry. Open and delete2 any branches that look like [Something\shell\*\command] and have a UNC path in the key. Mine was a program I used once on a Samba share that somehow made its way into my Open list.
Once I removed the offending key, it was back to business as usual.
1. nota bene: I did not intend for this to be a NirSoft shill post, but they really do have the two most useful tools for diagnosing Shell hook problems.
2. nota bene: if you aren't willing to live with toasting your Windows install, you may be inclined to export any keys you delete. I, however, am not so inclined.